For Argentina to have victory in the Falklands War, they would need to get Port Stanley airport, well the tarmac actually, to operate Skyhawk, Mirage, & Entendard aircraft. They also need more Exocett missiles. Achieving this would give the Argentines an unsinkable aircraft carrier & put the RN at a complete disadvantage.
Now if Britain was defeated, & it's a big if, the USA would have stepped in on the UK's side. Argentina's armed forces would have lasted about a day at best. Britain gets the Falklands back & Argentina still goes through a "revolution" where the military junta is kicked out etc. So, in the short term, little overall changes.
The mid to long term affects are very different.
Internationally, the UK's reputation would hit rock bottom. Obviously Maggie would be booted out of office, but that would be nothing compared to the depression that the UK would find itself in. The UK may even find itself to be the basket case of Europe. And, in relation to the EU, Britain would be considered a junior partner. France & Germany would both surpass the UK as a power - especially an economic one.